For some, playing videogames is just the beginning - the real fun is customizing them. Modders rethink characters, retool weapons, and repaint gigabytes of scenery to fashion a completely new experience. That's how the futuristic dystopias of the hit game Unreal Tournament 2004 became the gritty urban battleground of Red Orchestra: Combined Arms, a hyperrealistic replay of Europe's eastern front in World War II. No mere makeover, the total-conversion mod pushed Unreal's built-in scripting language to the limit, overhauling ballistics, damage, and basic movement to be truer to the laws of physics. The epic tweak consumed about 10 geek-years of work by a rotating crew of volunteers, who were in it mostly for the excitement of leaving their mark. Red Orchestra swept Nvidia's Make Something Unreal modding contest last year, winning $370,000 and the right to release a stand-alone commercial version. Just remember, guys: It's all fun and games until it becomes a real job.- Lucas Graves